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From Reinhard Poetz <>
Subject Re: [RT] Bidirectional relationships for blocks?
Date Wed, 30 Mar 2005 11:59:06 GMT
Daniel Fagerstrom wrote:
> Carsten Ziegeler wrote:
>> I might be wrong but I think up to now we only talked about one block
>> depending on another block and this is then a one-way relationship.
>> But what if we need a bidirectional relationship? I have currently two
>> examples:
>> a) Skins
>> We briefly talked about one use-case for blocks: skins. You factor out
>> the layout of your application into a skin block and then can simply
>> switch to a different block implementing the skin contract. Now, what if
>> the skin block needs some information from the "application block" like
>> some user settings or whatever?
>> b) Plugins or portlets
>> I could imagine to bundle portles for the cocoon portal engine as simple
>> blocks conforming to a cocoon portlet contract. So the portal block uses
>> the portlet blocks, but in addition a portlet block needs access to some
>> portal services.
>> The same would apply if you would use the block concept to implement
>> some kind of plugins.
>> Does this make sense? Or is this FS?
> The kind of polymorphism I have been talking about atacks exactly the 
> scenarios you describe. And from having used it in a number of 
> applications that I have been involved in developing during the last 
> year I can tell that it is a really convinient to reuse and extend e.g. 
> skins, in this way. There might be other design patterns for this, but I 
> have not seen any as smooth yet.
> /Daniel

I think we should stop discussing this topic in this theoretical way, at least I 
can't follow it anymore. I propose developing a *mock application* (contains 
only configuration files and pseudo code) that shows all the features of real 
blocks. Then we can decide what we need (not).

I will try to come up with something useful (I need it anyway for the 
block-deployer) within the next few days.

Reinhard Pötz           Independent Consultant, Trainer & (IT)-Coach 

{Software Engineering, Open Source, Web Applications, Apache Cocoon}


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